To fish using a karambwan vessel, players must first learn from Lubufu, an aged fisherman that lives near Brimhaven. Prior to finishing the quest, Karambwan can be caught only near Lubufu. After finishing it, however, this spot becomes inaccessible, and the vessel can be used only in eastern Karamja, near a Fairy Ring (combination D-K-P). For a vessel to work, a Raw karambwanji must first be placed inside to create the full karambwan vessel. There is a chance that the Karambwan will steal the Karambwanji without being caught.

Karambwan vessels are designed in such a way that a Karambwan can go in, but not get out. The neck of the vessel is far thinner than the body, which is shaped much like the body of a Karambwan. By placing dead Karambwanji in the vessel's rounded body, the fisherman can attract the Karambwan.

The Karambwanji is the Karambwan's favourite prey, but they are most commonly found in small inland bodies of freshwater. Because of this, a Karambwan will do almost anything to reach the fish, including climbing right into the body of the vessel. Once inside, the Karambwan cannot exit the vessel, its tentacles trapped with or behind it.

The design is not fool-proof, however, and often the Karambwan will manage to pull the bait from the body of the vessel without climbing fully in. Unfortunately, this annoyance is unavoidable.

Karambwan have long been a delicacy of the people of Karamja. However, they are extremely fast, very poisonous, and can escape most traps, making most conventional methods of capture useless. This has long made them a rare delicacy and a dangerous foe.

The origins of the vessel are unknown. Only a handful of fisherman have ever known of its design, and they have passed it on through their family for generations. Only they have ever been able to reliably catch the Karambwan. The current holder of this knowledge, Lubufu, is the last of his family, and has aged to the point where he can do little with the squid but sell them to The Shrimp and Parrot, a restaurant in Brimhaven.

During the Tai Bwo Wannai Trio quest, players convince Lubufu to teach them the secret of the Karambwan vessel, promising to tell no one of its design. After much convincing, Lubufu gives them the design. The player betrays him, however, and gives the information to Tiadeche, a tribal native. Lubufu's monopoly is ruined, and the process of Karambwan fishing becomes common knowledge in Karamja.